The present invention relates to the construction of micro-electromechanical systems and in particular discloses a method of manufacture of an out of plane bend actuator.
Recently, for example, in PCT Application No. PCT/AU98/00550 the present applicant has proposed an inkjet printing device which utilizes micro-electromechanical (MEMS) processing techniques in the construction of a thermal bend actuator type device for the ejection of fluid from a nozzle chamber.
In the utilization of bend actuators within (MEMS) devices, it is extremely important to have a highly efficient form of operation of the bend actuator. Unfortunately, the construction of (MEMS) devices often proceeds by the deposition and etching of multiple layers which in turn commonly results in a wafer surface, on a microscopic scale, becoming uneven and having a number of hills and valleys in accordance with the masking and etching of lower layers. Unfortunately, such hills and valleys are likely to have a substantial operational influence on any mechanical type devices such as a thermal actuator which is formed on top of a previously deposited substrate layer.
It is an object of the present invention to provide for an effective form of operation of (MEMS) mechanical devices such as bend actuators when formed on a substrate which is substantially non-planar at a microscopic level.
In accordance with a first aspect of the present invention, there is provided a moveable micromechanical device including a bend actuator adapted to curve in a first bending direction and having a substantially planar bottom surface, said bend actuator being formed on a plane substrate on top of a number of deposited lower layers, wherein the bend actuator is formed by a plurality of steps including:
forming a series of structures in said deposited lower layers, said series of structures having a surface profile including a series of elongate ribs running in a direction substantially transverse to said first bending direction.
The bend actuator can comprise a thermal bend actuator. The deposited layers can include a conductive circuitry layer and can be interconnected to the bend actuator for activation of the bend actuator. The bend actuator can be attached to a paddle member and actuated for the ejection of ink from an ink ejection nozzle of an inkjet printhead. The deposited layer, located under the bend actuator can include a power transistor for the control of operation of the bend actuator.